Automatically operable snap-acting switch



April 17, 1951 E. J. DILLMAN AUTOMATICALLY OPERABLE SNAP-ACTING swrrcn 3 Sheets-Sheet 1 Filed June 21, 1947 INVENTOR. f. 0M

ATTORNEY W BY April 17, 1951 E. J. DILLMAN AUTOMATICALLY OPERABLE SNAP-ACTING SWITCH Filed June 21, 1947 3 Sheets-Sheet 2 "l3 INVENTOR.

- ATTORNEY April 1951 E. J.'DILLMAN 2,548,877

AUTOMATICALLY OPERABLE SNAP-ACTING SWITCH 4) AITORNEY Patented Apr. 17, 1951 AUTOMATICALLY GPERABLE SNAP-ACTING SWITCH Earnest J. Dillman, Detroit, Mich., assignor to Detroit Lubricator Company, Detroit, Mich., a

corporation of Michigan Application June 21, 1947, Serial No. 756,265

31 Claims.

This invention relates to new and useful improvements in automatically operable snap acting devices.

An object oi this invention is to provide an improved snap switch which is automatically operable upon rise or fall of a physical condition above or below predetermined limits.

Another object of this invention is to provide an improved thrust linkage for an automatically operable snap acting device.

Another object of this invention is to provide an improved carrier mechanism for the switch contacts of a snap switch whereby vibration and chatter upon opening or closing motion may be substantially reduced or eliminated.

Another object of this invention is to provide an improved snap acting mechanism having an improved thrust linkage and being automatically responsive to changes in conditions afiecting the operating mechanism.

Other objects of this invention will become apparent from time to time through the specification and claims as hereinafter recited.

This invention consists of the new and improved construction and combination of parts to be more fully described hereinafter and the novelty of which will be particularly pointed out and distinctly claimed.

In the accompanying drawings, to be taken as a part of this specification, there are clearly and fully illustrated a number of preferred embodiments of this invention, in which drawings:

Figure l is a plan view of a device embodying this invention as applied to a pressure operated snap switch and having the casing cover member removed to show internal construction,

Fig. 2 is a sectional view taken along the line 22 of Fig. 1 having the cover member in place but having the insulating member end wall removed,

Fig. 3 is an enlarged sectional view taken along the line 33 of Fig. 2,

Fig. 4 is a sectional view taken along the line 44 of Fig. 3,

Fig. 5 is a detail sectional view taken along the line 5-5 of Fig. 2.

Fig. 6 is an enlarged sectional view taken along the line 66 of Fig. 1 but having the cover memher in place,

Fig. '7 is a view in side elevation and partly in section showing a modification of the invention operable by expansion of a thermo-expansive pellet,

Fig. 8 is a view in vertical section on the line 88 of Fig. 9 and showing another modification of the invention operable by direct fluid expansion,

Fig. 9 is a detail sectional view of the last mentioned modification and is taken along the line 59 of Fig. 8,

Fig. 10 is a detail sectional view of the last named modification and is taken along the line Ii -l0 of Fig. 9, and

Fig. 11 is a view in vertical section showing another modification of the invention operable by a thermo-sensitive bellows and applicable for use as a room thermostat.

Referring to the drawings by characters of reference in Figs. 1 to 6 there is an automatically operable snap switch I having an outer casing 2 with a cover member 3 secured thereto by screws 4. An inner casing 5 carries the main switch mechanism and is substantially covered along its bottom and end walls by a U shaped member 6 of an insulating material. The inner casing 5 and the U shaped insulating member 6 are secured each to each and to the bottom wall of the outer casing 2 by a plurality of screws or bolts t In the switch mechanism there are two pairs of electrical contacts, two of the contacts I being movable and the other two contacts 8 being fixed and carried by abutments 9 projecting downward from the upper wall H] of the inner casing 5. The movable contacts I are carried by a lever H which is bifurcated at one end and trifurcated at the other end. The lever l I is fabricated of a non-metallic insulating material, such as a laminated phenolic plastic, and has a metal U shaped flanged member l2 partially covering and enclosing the bifurcated end. The trifurcated end portion of the lever ll consists of two outer prongs l3 and an inner prong 14. A U shaped member l5 of hard resilient highly conducting material such as beryllium copper alloy is carried by the upper side of the lever l I and afiixed thereto by two rivets l6 and has its parallel legs ll extending longitudinally of the lever H from the outer prongs I 3 of the trifurcated end portion. The legs I! of the U shaped member l5 carry the movable contacts 1 and each terminates in a tongue portion l8. Positioned on and carried by the underside of the lever H is another U shaped member I9 afiired thereto by the rivets H5. The U shaped member l9 has two parallel leg portions 20 extending longitudinally of the lever II and termi nating in lip-turned end portions 2|. The legs 20 are offset from the lever H and inherently stressed downward from the lever H. The upturned end portions 2! have apertures 22 there-.

through which are operable to receive the tongue portions E8 of the legs I? of the U shaped member 55. The parallel legs 20 of the U shaped member is have holes 23 therethrough extending into the outer prongs it of the lever l i and operable to receive an adjustment member or screw 25 positioned therein. The adjustment screw 26 is operable upon movement to permit movement of the legs 25 downward thus tensioning the contact carrying legs H. The lever I i is pivoted on two fulcrum pins 25 extending through the wall of the inner casing into the downturned side portions of the flanged member l2. Adjacent the free end portion of the lever ii there is a bent arm portion or bracket member 26 which is carried by the upper wall portion l5 and affixed thereto by two rivets 27. The bracket 25 has an aperture 28 through its lower extremity and is operable to receive therein the tongue portion 29 extending from the center prong H! of the lever ii. The aperture 28 in cooperation with the tongue portion 29 functions as a stop member limiting the extent of travel of the lever ii. A magnetic armature 35 is carried by the center prong it of the lever i l and afiixed thereto. Carried by the upper wall it is a magnet 3i secured by a screw or bolt 32 to a screw-threaded member 35. The screw-threaded member 33 is threadedly connected to a drilled and tapped por tion 35 of an adjustment member 35 having an annular flange portion 35. The adjustment member 35 is screw-threadedly connected to a knob 3? bywhich upward and downward adjustment of the magnet 33! may be effected. A leaf spring 38 is mounted against the underside of the upper wall ill by a rivet 39 and has a bifurcated end portion 46 straddling the adjustment member 35 and engaging the upper face of the annular flange 35 and is operable to prevent rotation of the adjustment member 35 and the magnet 3i when the knob 3i is rotated and is further operable to hold the adjustment member 35 and magnet 58 in position as determined by the knob 3?. The knob 31 seats in and is rigid with a calibrated dial member 317 which seats against the upper face of the upper wall ii] and is limited in rotary movement by cooperation with a stop plate member 37 secured to the upper wall is by the rivets 2'5.v The switch carrying abutment ii is screw-threadedly connected to a bracket or molded insert ll (see Fig. 5) in the upper wall of the cover member to. Secured to the upper wall I 5 by each of the molded insert members ii is the flanged edge portion 52 of a shield member 33 made of electrical insulating material such'as a. laminated phenolic plastic. Also secured to the upper wall and by the insert member i! is a flanged bracket member id of a conducting material operable to receive a screw or bolt connection 65 for connecting the wire of an electrical circuit to the contact 8. The upper wall member I5 is secured to the inner casing 5 by screws 35 aflixing the wall 55 to a turnedin flange portion 3? of the casing 5. Two of the screws '65 also function to secure an extra cover member 58, of a thin insulating material to the upper wall member iii in overlying relation to the terminals 55.

Positioned in the aperture 48 formed by the bifurcated end portion of the lever ii and the U shaped flange member 12 is a swivel member 56, pivotally mounted on a fulcrum pin 5! extending laterally across the aperture 49 between the opposite walls of the downturned inner flange portion 52 of the'fiange member 12. The swivel tending partially member has an annular shoulder portion 53 around its upper edge and a similar portion 54 around its lower edge. The swivel member 50 also has a conical depression 55 centrally located in its lower face. A helical spring 55 is seated in the annular shoulder portion 53 of the swivel member 58 and is operable to urge the swivel member 55 downward thus rotating the lever H on its fulcrum. A irusto-conical cylindrical member 57 having an annular flange portion 58 and a longitudinal guideway 59 is positioned on the opposite end of the spring 55 from the swivel member 50. An adjustable threaded member 59 is screw threaded into a sleeve member 50 in the upper wall Iii of the casing 5 and has a screw threaded bore 5! extendin longitudinally therethrough. An adjustable screw 62 having a. cylindrical end portion 53 engages the member 5'? in the guideway 59 and is operable to determine the compression of the spring 56. Carried by and allixed to the upper end of the adjustment member 59 is a knob portion 54 having a calibrated dial plate 55 engageable with an indicator 35 carried by a bracket or angle member El secured to the upper wall iii by rivets 58. The indicator 65 is operable to limit rotary movement of the knob 6 by engagement with stop portions of the. dial plate 65.

The casing 5 has a lower wall 69 having an aperture "ill extending therethrough and through the lower wall i! of the outer casing 2. Positioned through the aperture 'iii and secured to the lower wall 69 of the inner casing 5 is a hollow connection member l2 having an internally threaded end portion l3 to receive a pressure line or conduit. Positioned in the upper end portion of the connection member '12 is a wall member '55 having a downturned flange portion 35 secured to the upper end portion as at '5. A screw threaded member E7 is adjustably positioned in the upper extremity of the threaded portion id of the connection member 72 and forms the bottom wall of a chamber "E8. The wall member 14 has an aperture'lil interconnecting the chamber '18 and the interior of the casing 5 and has a plunger member 85 positioned therein. The plunger member 8!] is substantially cylindrical in form, having a hollow portion exlongitudinally therethrough and having a flanged portion 8! at its lower extremity and terminating in an extended conical tip 82 at its upper extremity. The conical tip 82 is positioned in engagement with the conical recess 55 in the swivel member 58, A cylindrical metal bellows or pressure responsive member 83 is sealed to the wall 76 in the aperture 19, surrounds the plunger 80 and is sealed to the flanged portion 85. A helical spring 8 is positioned in the hollow portion 55 of the plunger and is compressed between the upper wall 86 of the hollow portion 85 and the upper face of the screw threaded member ll which may be provided with a lock nut. The screw threaded member ll has an aperture 85 interconnecting the threaded end portion 53 and the chamber portion 78 of the connection member 12 and is operable to permit pressure such from a steam line to enter the chamber is and actuate the bellows 83 and plunger 35.

In operation this form of the invention functions as follows:

In its initial state the switch contacts 'l and 8 are normally open, the spring 55 urging the lever i i toward its open position and the inherent resilience of the bellows 83 and the spring 84 being operative to resist this movement by the spring 56. When gaseous pressure such as from a steam line is supplied to the chamber 18 of the connection member 12 the bellows 83 is compressed and the plunger moves longitudinally upward against the swivel member 50 thus causing the lever H to rotate toward switch closed position. When the pressure has caused the plunger 80 to move the lever H upward a distance sufficient to permit an appreciable attraction between the ma net 3| and the armature 30 the attractive force of the magnet 3| acting in cooperation with the pressure operated bellows 83 will be sufficient to overcome the force of the upper spring 56 and cause the switch contacts 1 and 8 to close with a snap action. Conversely, when the pressure operating the switch is decreasing, the magnet 31 will hold the contacts closed after the pressure operating the bellows S3 is no longer strong enough of itself to resist movement by the spring 56 and when the combined force exerted by the pressure on the bellows 83 and the magnetic attraction between the magnet 3i and the armature 30 becomes less than the force exerted by the spring 56 the contacts I and 8 will then open with a snap action. It should be noted that the bracket member 26 and its aperture 28 cooperating with the tongue portion 29 of the lever I I will prevent any further application of force upon the contacts 1 and 8 when in closed position and functions as a limit stop for opening and closing movement of the lever l I. When the switch contacts 1 are in open position the resilient member I! is tensioned by the tongue portion l8 which extends through the aperture 2! of the other U shaped member 9. When the switch contact 1 closes against the contact 8, the tongue portion I8 is moved out of engagement with the member 20 and the contact 1 is tensioned against the contact 8 by the resilience of the arm I! of the U shaped member l5 functioning as a cantilever spring. Upon opening movement the upturned flange portion 21 of the U shaped member 26 again engages the tongue portion l8 and tensions the resilient arm I! thus preventing vibration or chatter on this opening movement. The amount of tension desired in the contact-carrying arm I! may be adjusted by the screw 24 by which the arm 28 of the U shaped member 19 may be permitted to move downward. The air gap distance between the magnet 31 and the armature 30 when the switch contacts are closed may be adjusted by the knob 31; this adjustment of the magnetic air gap distance will determine the amount of travel by the lever H necessary to cause the switch to close with a snap action. This adjustment of magnetic air gap distance has the further function of determining the differential of pressure between that required to open or to close the switch. The magnet 3| has the additional function of maintaining the switch contacts tensioned against each other in closed position. The compression of the spring 56 may be adjusted by the knob 64 thus determining the force required in opposition to the spring 56 to close the switch contacts 1 and 8. The screw threaded member 11 bearing against the spring 84 is operable upon adjustment to determine the force exerted by the spring 84 and the bellows 83 against the upper spring 56. It should be noted that the operation of this pressure operated switch is especially adaptable for use as an alarm switch for registering the efiect of excessive rise of pressure in a gas line or more especially in a steam line.

In the form of the invention shown in Fig. '7 there is a snap switch which is adapted to respond to changes of temperature. The essential elements of this switch (e. g. the lever, resilient contact carrying arm, the swivel member, the spring 56 bearing against the swivel member etc.) are common to all forms of the invention shown throughout the various drawings and all common parts ar given t same reference numerals as in the principal form of the invention illustrated in Figs. 1 to 6. The principal difference between the principal form of this invention and that shown in Fig. '7 is that the modification shown in Fig. '7 is adapted to respond to a thermal sensitive element. There is a connection member 81 positioned through the lower wall 69 of the easing 5 which corresponds to the member 12 in the principal form of the invention. The connection member Bl is externally threaded as at 88 to provide a screw connection for mounting to the object to be controlled (such as a hot water or steam boiler). The member 8'! has a longitudinal passageway therethrough of a large bore 89 at its upper end, a smaller bore 90 at its lower end and a small passageway 9i interconnecting the bores 89 and 9B. Extending from the lower bore portion 90 is a conduit or supporting member 92 having therein a cylindrical member 93 with a flange portion 94 at its lower end. The cylindrical member 93 has an internal bore 95 with a plug member 96 of a rubber or rubberlike material. Positioned below the flange 84 is a cup-shaped member 9? having a flange portion 98. The cup-shaped member 9'! is joined by its flange portion 93 to the flange portion 94 and held in position by an annular flanged member 99 and having a diaphragm member Hi8 positioned between the flanges 94 and 98 and closing the open end of the member 9? just below the plug member 96. The diaphragm member Hill and the cup-shaped member 8i form a closed chamber having a thermal responsive material lfil therein. The thermal responsive material liil is preferably formed of a mixture of waxes which have a high rate of expansion when changing from the solid to liquid state or may be of a composition such as is disclosed by Patent 2,259,846 issued to Sergius Vernet. Positioned in the bore 95 of the cylindrical member 93 and seating on the plug 96 is a piston 152 which has a flanged stop portion Hi3 and bears against a plunger its which extends through the longitudinal passageway or bores 89 and 90 and is guided in and through the bore 9! and terminates in an annular shoulder portion I05. Seated on the annular shoulder portion ".15 is a flanged disc member I95 having a helical spring IE1 seating thereagainst, the spring H)? seating at its other extremity on the annular shoulder portion 55 of the swivel member 50. Other changes from the principal form of the invention are only minor details of con struction.

In this form of the invention there is no outer casing 2 but the inner casing 5 is closed at its end portions by a U shaped member Hi8 held in position by screws or bolts 199. carried directly by a screw-threaded member or bolt llll having a stop nut H! and adjustable by use of a screwdriver or other means instead of a knob 31. Similarly the adjustment of the compression of the spring 53 is effected by the screw member or bolt 62 instead of the knob 64 and has a stop nut H2 to secure the bolt 52 in position.

In operation thi form of the invention functions as follows:

The magnet 3| is 2 When the temperature of the thermal. responsive material IEI is increased, the material expands and exerts force through .the diaphragm I and-plug 95 against the piston m2 and the plunger I04.

I0! to the swivel member '59 causing the lever I l to be rotated towards contact closed position. When the lever l l is rotated a sufficient distance that the combined force of themagnet 3i acting upon the armature 3B and the force of the. spring Ill! is greater than the force exerted by the spring 56 the switch will snap closed. Similarly upon fall of temperature the magnet 3! will hold the switch contacts I and 3 closed until the combined force of the magnet 3! and the spring it! become less. than the force exerted by the spring 56. The attraction of the magnetfil as above described will determine the differential between the temperatures required to open or to close the switch. As in the main form of the invention, the switch contact carrying arms I! are tensioned by the member'ZG so as to prevent vibration or chatter upon opening and closing the switch contacts.

It should be notedthat in all forms of this invention heretofore and hereafter described the switch can be made to operate in reverse by moving the fulcrum-point for the lever l I to the opposite side of the fulcrum point for the swivel member 5flthan that described so that a rise of temperature or pressure will cause the switch contacts to operate in a reverse'direction from that shown. It should be further noted that for the magnet to be able to pull the contacts closed with a snap action there-must'not be an appreciable decrease in force, applied in opposition to the sprin 56 uponsudden movement of the lever ll since the magnet is not sufficiently strong to holdthe contacts closed against the force of the spring 56. If the means transmitting the force to the swivel member-5e in opposition to the spring 56- is a solid incompressible means then the force applied to that means must be compressible for otherwise a slight movement of the force transif liquid pressure wereapplied to this formof the invention there could never bea snap action.

because a veryslight movement of the lever away-from theplunger 80 would cause a reduce tionin pressure against the plunger 85 substantially to zero. Conversely it is seen-that if..the force .actuatingthe leverinopposition to-.the. springxfisis of anincompressibletype such.

as caused by vliquid or olid expansionthen the,

means transmittin that'foree must be comprese sible suchas -the spring I5! in Fig. 7.. In this. form as the temperature rises. the thermal res.

sponsive material iii! expands providing an-ins compressible source of force for-actuating the-nlever I I. This forceis transmitted throughuthe spring Illl'to the swivel member Ed'sothat when the lever ll moves within; the force of attraction of the magnet 3| the slight closing movement of the switch will not cause an appreciablereduction As the plunger lll l moves upward, this movement i transmitted throughthe spring ing-movement of the lever ll- Also in this form randfunction as heretofore described.

in the. compressive force exerted by, the spring; Ill'l. It should be further noted that in both basic forms :of :this. invention the increaseof attractive forceof themagnet 3| upon closing movement in cooperation with opposing force to:overcome the. force of the spring 56..

In the form of the invention shown in Figs. 8, 9 and 10, the switch mechanism is essentially that shown and described in Fig. 7 but adapted for response to fluid expansion (either expansion-bypressure or thermal expansion).- and the.

modifications from the form shown in Fig. '7 are only slight.

As pointed out heretofore, all parts which are.

common are given common reference characters form shown in Fig. 8 there is an outer casing2 enclosing the switchmechanism and inner casing 5 which is secured thereto by a screwor bolt member H3, the outer casing 2 having a cover rnember 3 secured thereto by screws or bolt members l. There is an elongated-connection member H4 which is externally threaded as at '5 for mounting and receives at its lowerendaconduit H5 operable to transmit expansive -force of a liquid to the responsive mechanism of the switch. There is a large bore portion 89 in the upper end of the connection memberll i and a smaller threaded bore portion l l? immediately therebelow which is operable to receive a threaded hollowcylindrical plug member 5 [8. A small'bore or longitudinal passageway 5 l9 interconnects the end portion receiving the conduit H6 and the threaded bore portion i ll. There is an expansive diaphragm or pressure responsive sealing member lit of a rubber-like material which is sealed to an internal annular shoulder [2| by the threaded plug member l 18 and is operable to form an expansible chamber E22 for receiving fluid under pressure from the conduit H6 and the passageway I [9. Seating on its lower endon the sealing-member H0 is a plunger lll l having an annular shoulderill5 with a flange disc member Hit seating thereon. A spring I0? is positioned between the-flange disc member Id e and the annular shoulder 54 of the swivel member and is operable to transmit thrust therebetween. There are some slight changes in the structure of the lever and switch mechanism which will be enumerated hereinafter. The lever is fulcrumed on the fulcrum pin 523 (see Fig. 9) extending'from wall'to wall across the casing 5 and passing through an enlarged aperture I24'(see Fig. 8) in the swivel member 59. changes include theuse of knobs and calibrated dials as in Figs. 1 to 6 on the screw mechanism for'adjustment of magnetic gap and compression of the-spring 55." In this form, however, the indicator H5 is located between the two knobs instead of between the spring adjustment knob and end of casing as in Fig. 3. member 26is replaced bya cylindrical rod I26 having. an annular groove .22? therein between. the shoulders .ofwhich is positioned. the tongue.

portion 29. .of -the'lever l I. The shoulders of the groove --.i2l are-operable as limit stopsfor -limit oftheinvention the contact carrying arms 11 are :tensioned by the member [Shut the adjust-1 ment screw N has been eliminated so that. there:

In the Other minor The bracket stop is no adjustment of the amount of tension in the contact carrying arms.

In operation this form of the invention functions similarly to the form illustrated in Fig. '1 and by pressure transmitted through the conduit IIS and the passageway II9 to the chamber or space I22. This fluid under pressure being operable upon expansion or movement to move the plunger I [I4 thus transmitting force or movement through the spring I81 to the lever I I for moving the switch contacts 1 to closed position as shown. The adjustment of the magnet and of the spring 53 is by the knobs 31 and 64 respectively, these adjustments being operable to determine the pressure or amount of movement of fluid necessary to close said switch. As in the previous form there is an incompressible force transmitted through a compressible force transmitting means (the spring I01) and operable to move the lever II; as pointed out heretofore the operation of an incompressible force through a compressible transmitting means or a compressible force through an incompressible transmitting means makes it possible to produce a sensitive switch mechanism that is snap acting.

In the form shown in Fig. 11 there is a modification of the principal form of the invention similar to that shown in Figs. 1 to 6 in which a pressure responsive bellows I28, which is similar to the responsive bellows 83 (shown in Fig. 6) but is completely enclosed and is responsive to changes in pressure caused by expansion and contraction of a thermal responsive gas or volatile liquid enclosed therearound. This form of the invention is adaptable particularly to use as a room thermostat. There is an outer casing I29 having a removable end wall I30 and cover plate I3I. The end wall I38 is secured to the casing I29 by screws I32 and the cover member I3I is secured to the end Wall I33 by a screw I33. The inner casing 5 is secured to and carried by the end wall I 30. As heretofore pointed out the parts of this form of the invention which are common to the others are given the same reference characters and are assembled substantially as heretofore described. There is a plunger 89 having a conical tip portion 82 which bears against the conical depression 55 in the swivel member 53. The plunger 8!] is also surrounded by and fixed to the end wall of the pressure responsive bellows I as was the plunger 80 in Fig. 6. There is a cup-shaped member I34 enclosing the bellows I 28 and closed by an end member I of a non-metallic material and having an aperture 5 therethrough for longitudinal movement of plunger 58 An annular flange member I31 is sealed to the cup-shaped member I34 and to the bellows I23, the bellows I28 and cup-shaped member I34 enclosing a chamber portion I33 in which is contained the aforementioned thermal responsive gas or volatile liquid. The cup-shaped member I34, bellows I28, end member I35 and plunger w are carrier by the end wall member and spaced therefrom by a plurality of posts I In this modification the adjustment of the magnet is by an adjustment screw or bolt I I5 and lock nut I i! as was shown in Fig. 7. The essential difference in this form of the invention is the change in the mechanism for adjusting the tension of the spring 55 whereby the temperature at which the switch will respond may be more easily adjusted. There is a saddle shaped member carried by the upper wall I!) and secured thereto by the screw or bolt 46 extending through the flange portion I and the wall portion I0 into the inturned flanged portion 41 of the side wall of the inner casing 5. There is a flange disc member 51 engaging the spring 55 as in the other forms of the invention but in this form the member 51 has a bore I II passing centrally therethrough in which is positioned a cylindrical rod I42 along which the member 51 may have longitudinal movement, the rod I42 being secured to and carried by the saddle member I39. The sa dle member I39 terminates at one end in a pair of projecting portions I43, only one being shown,

each having a pointed portion I44 cooperatively engaging side edge projecting arms I45 from a lever I45 and functioning as a fulcrum point therefor. The lever I45 has an aperture I41 therethrough and spaced projecting portions I48 which engage the face of the disc member 51 and are operable upon movement to move the disc member 51 longitudinally along the rod I42 thereby adjusting the compression of the spring 55. Cooperable with the lever I45 there is a lever member I49 having a turned-down edge or flange portion I50 and fulcrumed on a pin I5I which is carried by the end wall I35. A screw threaded adjustment member I52 is screw threadedly positioned through and operable to move the lever I49 and has a knob portion I53 of a non-metallic material. The adjustment screw I52 is screw threadedly positioned through the lever I49 and bears against the end wall I35 and is operable upon rotary movement to move the lever I49 about its fulcrum I5I. The screw I52 carries an indicator disc I53 viewable through a window opening I53 and having edge stops cooperable with a rotation limiting member I53 The levers I49 and I45 have slots or apertures I54 and I55 respectively through and between which is positioned a thrust rod I53 in the form of a channel member having tongue portions I51 and I58 extending through the aforementioned apertures and through an aperture I59 in the end wall I30 and operable to transmit thrust between the lever I 49 and the lever I 45. It should be noted then from the aforementioned construction that movement of the adjustment knob I53 will be transmitted through the lever I45 and the thrust rod I56 and the lever I45 to the spring 55 thereby controlling the compression of the spring 55 and determining the force required to open the switch which in this case would be the temperature to which this device would respond. In commercial applications the knob I53 and mechanism interconnected therewith would be calibrated for adjustment to room temperatures to which this thermostatic switch would respond. In all other features this device is substantially as described heretofore in the other forms.

In operation this form of the invention functions as a thermostat responsive to changes in room temperature. When the temperature in the chamber I35 increases, the pressure therein increases causing the bellows I25 to move the plunger Gil against the opposition of the spring 55 thus causing the switch contacts to open (this form being as suggested heretofore that the fulcrum point for the lever II is on the opposite side of the fulcrum point for the swivel member as compared to the other forms of this invention) When the temperature decreases, the bellows 523 will expand permitting the switch contacts to close with a snap action thus reenergizing the circuit and the heat unit controlled by this thermostat. For adjustment of temperature at which this device will respond, the movement of the knob 553 will transmit movement through the levers 1 39, M5 and the thrust member 15% to the spring thereby determining the compression of the spring 56 and the temperature at which this switch will respond. It should be noted that a feature common to all forms of the invention shown is the arrangement of the spring 56 relative to the opposing force on opposite side of the swivel member 59. In each of the forms of the invention the lever H is shiftable slightly on its fulcrum within the limits of the inner casing 5 and the opposing forces acting upon the swivel member 5!) are diametrically opposed and substantially equal so that they function to keep the lever l l centered on its fulcrum and thereby reduce the possibility of friction by the edges of the lever ll against the side walls of the inner casing 5. It should be further noted that the form of transmitting force through one spring and a swivel member against an opposing spring to provide movement for a lever is not restricted to the opening and closing of switch contacts but could be used in many forms of control devices such as for the opening and closing of a valve stem operable by the lever l i.

What is claimed and is desired to be secured by Letters Patent of the United States is:

1. In a switch, a pair of switch contacts, one of said contacts being movable, the other of said contacts being fixed, a lever carrying said movable contact, stop means cooper'able with said lever and operable to determine the limits of travel of said lever, said lever having an aperture through one end, a swivel member pivotally carried by said lever in said aperture, spring means engageable with said swivel member and operable to urge said lever in one direction, means alined with and engaging said swivel member in opposition to said spring means and operable to urge said lever in the opposite direction, and tensioned resilient means carried by said lever and carrying said movable contact so that said switch may open or close without appreciable vibration.

2. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being movable, the other of said contacts being fixed, a lever carrying said movable contact, means operable to cause said lever to open and to close said switch with a snap action, stop means cooperable with said lever and operable to deteremine the limits of travel of said lever, said lever having an aperture through one end, a swivel member pivotally carried by said lever in said aperture, spring means engageable with said swivel member and operable to urge said lever in one direction, means alined with and engaging said swivel member in opposition to said spring means and operable to urge said lever in the opposite direction, and tensioned resilient means carried by said lever and carrying movable contact so that said switch may open or close with a snap action without appreciable vibration.

3. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being movable, the other of said contacts being fixed, a lever carrying said movable contact, operable to cause'said lever to open and to close said switch with a snap action, stop co-- operable with said lever and operable determine the limits of travel of said lever, said lever having an aperture through one end, a swivel member pivotally carried by said lever in said aperture, spring means engageable with said said swivelmember and operable to urge said lever in one direction, means alined with and engaging said swivel member in opposition to said spring means and operable to urge said lever in the opposite direction, tensioned resilient means carried by said lever and carrying said movable contact so that said switchmay open or close with a snap action without appreciable vibration, and said first-named means being further operable to hold said resilient contact carrying means tensioned against said fixed contact when said switch is closed.

4. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being movable, the other of said contacts being fixed, a lever carrying said movable contact, means at each side of said lever operable to support the levers fulcrum, said lever being shiftable slightly laterally on its fulcrum, means to cause said switch to open and to close with a snap action, said last-named-means also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, spring means urging said lever in one direction, a second spring means operable to urge said lever in the opposite direction, automatically operable means for supplying force to said second-named spring means, and said first-named and said second spring means being alined with and diametrically opposed to each other thereby acting to center said lever on its fulcrum and thus reduce side friction between said lever and said supporting means.

5. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being movable, the ether of said contacts being fixed, a lever carrying said movable contact, means at each side of said lever operable to support the levers fulcrum, said lever being shiftable slightly laterally on its fulcrum, means to cause said switch to open and to close with a snap action, said last-named means also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed,

r spring means urging said lever in one direction,

means responsive to the restricted movement of an incompressible fluid under pressure, a second spring means for transmitting force from said last-named means to said lever and acting in opposition to said first-named spring means, and said first-named and said second spring means being alined with and diametrically opposed to each other thereby acting to center said lever on its fulcrum and thus reduce side friction between said lever and said supporting means.

6. In an automatically operable snap switch, a pair of switch contacts, one 01" said contacts being movable, the other of said contacts being fixed, a lever carrying said movable contact, means at each side of said lever operable to support the levers fulcrum, said lever being shiftable slightly laterally on its fulcrum, means to cause said switch to open and to close with a snap acticn, said last-named means also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, spring means urging said lever in one direction, means responsive to the pressure of a compressible fluid, a second spring means cooperable with said lastnamed means and acting therewith. in opposition to said first-named spring means, said second spring means and said pressure responsive means being operable to urge said lever in the opposite direction; and said first-named spring means, and said second spring means and pressure re- 13 sponsive means, being alined with and diametrically opposed to each other thereby acting to center said lever on its fulcrum and thus reduce side friction between said lever and said support ing means.

7. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being movable, the other of said contacts being fixed, a lever carrying said movable contact, means for supporting the fulcrum of said lever positioned to each side thereof, said lever being shiftable slightly laterally on its fulcrum, a magnetic armature carried by said lever, a magnet for attracting said armature and operable to cause said switch to open and to close with a snap action, said magnet also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, spring means urging said lever in one direction, means urging said lever in the opposite direction, said lastnamed means including means responsive to expansive movement of a liquid under pressure and including a second spring means, said second spring means being alined with and diametrically opposed to said first-named spring means thereby acting to center said lever on its fulcrum and thus reduce side friction between said lever and said supporting means, and means for adjusting the compression of said first-named spring means thereby to determine the condition to which said switch will respond.

8. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being fixed, the other of said contacts being movable, a lever carrying said movable contact, an armature carried by said lever, a magnet for attracting said armature and operable to cause said switch to open and to close with a snap action, said magnet also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, a spring urging said lever in one direction, an adjustable abutment for adjusting the compression of said spring, a plunger bearing against said lever in opposition to said spring, a metal bellows surrounding said plunger and affixed to said plunger at one end, said bellows functioning as a spring in opposition to said first-named spring, a spring bearing against said plunger, an adjustable abutment for adjusting the compression of said second spring, said second spring eing adjustable to determine the tension against said first spring, said plunger and bellows being responsive to the application of gaseous pressure thereto thereby to actuate said lever, and said first spring being adjustable to determine the pressure to which said switch will respond.

9. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being fixed, the other of said contacts being movable, a lever carrying said movable contact, an armature carried by said lever, a magnet for attracting said armature and operable to cause said switch to open and to close with a snap action, said magnet also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, a spring urging said lever in one direction, an adjustable abutment for adjusting the compression of said spring, a second spring urging said lever in the opposite direction, said second spring being alined with and diametrically opposed to said first spring and of substantially the same strength as said first spring, liquid expansion responsive means for transmitting movement to said second spring and said lever, a plunger operatively connecting said liquid expansion responsive means and said second spring, said liquid expansion responsive means being operative to actuate said lever, and said first spring being adjustable to determine the condition to which said switch will respond.

10. In an automaticall operable snap switch, a pair of switch contacts, one of said contacts being fixed, the other of said contacts being movable, a lever carrying said movable contact, means operable to cause said switch to open and to close with a snap action, said means also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, a spring urging said lever in one direction, an adjustable abutment for adjusting the compression of said spring, a second spring urgin said lever in the opposite direction, aid second spring bein alined with and diametrically opposed to said first spring and of substantially the same strength as said first spring, liquid expansion responsive means for transmitting movement to said second spring and said lever, a plunger operatively connecting said liquid expansion responsive means and said second spring, said liquid expansion responsive means being operative to actuate said lever, and said first spring being adjustable to determine the condition to which said switch will respond.

11. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being fixed, the other of said contacts being movable, a lever carrying said movable contact, an armature carried'by said lever, a magnet for attracting said armature and operable to cause said switch to open and to close with a snap action, said magnet also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, a spring urging said lever in one direction, an adjustable abutment for adjusting the compression of aid spring, a second spring urging said lever in the opposite direction, said second spring being alined with and diametrically opposed to said first spring and of substantially the same strength as said first spring, thermal expansion means for transmitting movement to said second Spring and said lever, said thermal expansion means being operative to actuate said lever, and said first spring being adjustable to determine the temperature to which said switch will respond.

12. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being fixed, the other of said contact being movable, a lever carrying said movable contact, an armature carried by said lever, a magnet for attracting said armature and operable to cause said switch to open and to close with a snap action, said magnet also functioning to hold said movable contact tensioned against aid fixed contact when said switch is closed, a spring urging said lever in one direction, an adjustable abutment for adjusting the compression of said spring, a plunger bearing against said lever in opposition to said spring, a metal bellows surrounding said plunger and afiixed to said plunger at one end, said bellows functioning as a spring means in opposition to said first-named spring, a spring bearing against said plunger, an adjustable abutment for adjustin the compression of said second-named spring, said second-named spring being adjustable to determine the force counterbalancing said first-named spring; said plunger, said bellows, and said second-named spring being alined with and diametrically opposed to said first named spring and exerting substantially the same force against said lever as said first named spring; said plunger and bellows bein responsive to the application of gaseous pressure thereto thereby to actuate said lever, and said first-named spring being adjustable to determine the pressure to which said switch will respond.

13. In an. automatically operable snap switch, a pair of switch contacts, one of said contacts being movable, the other of said contacts being fixed, a lever, a resilient member carried by and affixed to said lever and carrying said movable contact, means carried by said lever and operable to tension said resilient member, means to adjust the tension of said resilient member, said tensioned resilient member bein operable to prevent vibration on opening or closing of said switch, means to cause said switch to open and to close with a snap action, said lastmamed means also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, sprin means urging said lever in one direction, and means operable to urge said lever inth-e opposite direction.

14. In an automatically operable snap switch, a pair oi switch contacts, one of said contacts being movable, the other of said contacts being fixed, a lever, a resilient member carried by and afiixed to said lever and Carrying said movable contact, means carried by said lever and operable to tension said resilient member, means to adjust the tension of said resilient member, said tensioned resilient member being operable to prevent vibration on opening or closing of said switch, means to cause said switch to open and to close with a snap action, said last-named means also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, spring means urging said lever in one direction, and means including pressure responq sive means and a second spring means operable to urge said lever in the opposite direction.

15. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being movable, the other of said contacts being fixed, a lever, a resilient member carried by and afixed to said lever and carrying said movable contact, means carried by said lever and operable to tension said resilient member, means to adjust the tension of said resilient member, said tensioned resilient member being operable to prevent vibration on opening or closing of said switch, means to cause said switch to open and to close with a snap action, said last-named means also functioning to hold said movable contact tensioned. against said fixed contact when said switch is closed, spring mean urging said lever in one direction, second spring means operable to urge said lever in the opposite direction, and means responsive to the restricted movement of a liquid under pressure and operable to transmit force to said second spring means and said lever.

16. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being fixed, the other of said contacts being movable, a lever, a resilient member carried by and amxed to said lever and carrying said movable contact, means carried by said lever and operable to tension resilient member, means to adjust the tension of said resilient member, said tensioned resilient member being operable to prevent vibration on opening or closing of said switch, an armature carried by said lever, a magl 6 net for attracting said armature and operable to cause said switch to open and to close with a snap action, said magnet also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, a spring urging said lever, in one direction, an adjustable abutment for adjusting the compression of said spring, a plunger bearing against said lever in opposition to said spring, a metal bellows surrounding said plunger and affixed to said plunger at one end, said bellows functioning as a spring in opposition to said spring, a spring bearing against said plunger, an adjustable abutment for adjusting the compression of said second spring, said second spring being adjustable to determine the tension against said first spring, said plunger and bellows being responsive to the application of gaseous pressure thereto thereby to actuate said lever, and said first spring being adjustable to determine the pressure to which said switch will respond.

1?. In an automatically operable snap switch, a of switch contacts, one of said contacts being fixed, the other of said contacts being movable, a lever, a resilient member carried by and affixed to said lever and carrying said movable contact, means carried by said lever and operable to tension said resilient member, means to adjust the tension of said resilient member, said tensioned resilient member being operable to prevent vibration on opening or closing of said switch, means operable to cause said switch to open and to close with a snap action, a spring urging said lever in one direction, an adjustable abutment for adjusting the compression of said spring, a plunger bearing against said lever in opposition to said spring, a metal bellows surrounding said plunger and airlxed to said plunger at one end, said bellows functioning as a spring in opposition to said spring, a spring bearing against said plunger, and adjustable abutment for adjusting the compression of said second spring, said second spring being adjustable to determine the tension against said first spring, said plunger and bellows being responsive to the application of gaseous pressure thereto thereby to actuate said lever, and said first spring being adjustable to determine the pressure to which said switch willrespond.

18. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being fixed, the other of said contacts being movable, a lever, a resilient member carried by and affixed to said lever and carrying said movable contact, means carried by said lever and operable to tension said resilient member, means to adjust the tension of said resilient member, said tensioned resilient member being operable to prevent vibration on opening or closing of said switch, an armature carried by said lever, a magnet for attracting said armature and operable to cause said switch to open and to close with a snap action, said magnet also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, a spring urgsaid lever in one direction, an adjustable abutment for adjusting the compression of said spring, a second spring urging said lever in the opposite direction, said second spring being alined with and diametrically opposed to said first spring and of substantially the same strength as said first spring, liquid pressure expansive means for transmitting movement to said second spring and said lever, a plunger operatively connecting said liquid pressure expansive means and said second spring, said liquid pressure expansive means being operative to actuate said lever, and said first spring being adjustable to determine the condition to which said switch will respond.

19. In an automatically operable snap switch, a pair of switch contacts, one of said contacts being fixed, the other of said contacts being movable, a lever, a resilient member carried by and afiixed to said lever and carrying said movable contact, means carried by said lever and operable to tension said resilient member, means to adjust the tension of said resilient member, said tensioned resilient member being operable to prevent vibration on opening or closing of said switch, an armature carried by said lever, a magnet for attracting said armature and operable to cause said switch to open and to close with a snap action, said magnet also functioning to hold said movable contact tensioned against said fixed contact when said switch is closed, a spring urging said lever in one direction, an adjustable abutment for adjusting the compression of said spring, a plunger bearing against said lever in opposition to said spring, a metal bellows surrounding said plunger and affixed to said plunger at one end, said bellows functioning as a spring means in opposition to said first-named spring, a spring bearing against said plunger, an adjustable abutment for adjusting the compression of said second-named spring, said second-named spring being adjustable to determine the fo ce counterbalancing said first-named spring; said plunger, said bellows, and said second-named spring being alined with and diametrically opposed to said first-named spring and exerting substantially the same force against said lever as said first spring; said plunger and bellows being responsive to the application of gaseous pressure thereto thereby to actuate said lever, and said first spring being adjustable to determine the pressure to which said switch will respond.

20. In an automatically operable snap switch, two pairs of switch contacts, two of said contacts being fixed, the other two of said contacts being movable, a lever carrying said movable contacts, said lever being of an insulating material, bifurcated at one end and trifurcated at the other end, a metal U shaped flanged portion partially covering and enclosing the bifurcated end of said lever, said lever being fulcrumed on said metal flange portion and shiftable slightly laterally, a casing enclosing said contacts and said lever and carrying the fulcrum for said lever, a U shaped resilient strip of metal carried by the outer prongs of said trifurcated end portion and carrying said movable contacts, a member having an upturned end portion carried by and affixed to the underside of each of outer prongs of said trifurcated end portion, said upturned end portions having an aperture therethrough receiving the end portion of said resilient metal strips. an adjustment member extending through said member into said outer prongs whereby said member may be adjusted as to tension said resilient metal strip, a magnetic armature carried by the center prong of said trifurcated end portion, a magnet for attracting said armature, said magnet being operable to cause said switch contacts to open and to close with a snap action, said magnet being further operable to cause said movable contacts to be tensioned against said fixed contacts when said switch contacts are closed, a swivel member carried between the prongs of said bifurcated end portion, a spring positioned against said swivel member and urging said lever in one di rection, an adjustable abutment for adjusting the compression of said spring, a plunger positioned against said swivel member in opposition to said spring, a metal bellows surrounding said plunger and aflixed to one end thereof, said bellows functioning as a spring means in opposition to said spring and urging said lever in the opposite direction, a spring bearing against said plunger, an adjustable abutment for adjusting the compression of said second-named spring, said second-named spring being adjustable to determine the initial force exerted against said first spring; said plunger, said bellows, and said second-named spring being alined with and diametrically opposed to said first-named spring and exerting substantially the same force against said swivel member as said first spring thereby functioning to center said lever on its fulcrum so as to reduce side friction be tween said lever and said casing, said plunger and bellows being responsive to the application of gaseous pressure thereto thereby to actuate said lever, an adjustable abutment carrying said magnet, said magnet being adjustable as to vary the tension of the contacts when closed and to vary the amount of travel of said plunger necessary to cause said contacts to snap open or to snap closed, and said first spring being adjustable to determine the pressure to which said switch will respond.

21. In an automatically operable snap switch, two pair of switch contacts, two of said contacts being fixed, the other two of said contacts being movable, a lever carrying said movable contacts, said lever being of an insulating material, bifurcated at one end and trifurcated at the other end, a metal U shaped flanged portion partially covering and enclosing the bifurcated end of said lever, said lever being fulcrumed on said metal flange portion and shiftable slightly laterally, a casing enclosing said lever and said contacts and carrying the fulcrum of said lever, a U shaped resilent strip of metal carried by the outer prongs of said trifurcated end portion and carrying said movable contacts, a member having an upturned end portion carried by and afiixed to the underside of each of outer prongs of said trifurcated end portion, said upturned end portions having an aperture therethrough receiving the end portion of said resilient metal strips, an adjustment member extending through said member into said outer prongs whereby said member may be adjusted as to tension said resilient metal strip, a magnetic armature carried by the center prong of said triiurcated end portion, a magnet for attracting said armature, magnet being operable to cause said switch contacts to open and to close with a snap action, said magnet being further operable to cause said movable contacts to be tensioned against said fixed contacts when said switch contacts are closed, an adjustable abutment carrying said magnet, said magnet being adjustable as to vary the tension of the contacts when closed and to vary the amount of travel of the means operating said lever necessary to cause said contacts to snap open or to snap closed, a swivel member carried between the prongs of said bifurcated end portion, a spring positioned against said swivel member and urging said lever in one direction, an adjustable abutment for adjusting the compression of said spring, a second spring positioned against said swivel member in opposition to said first-named spring and urging said lever in the opposite direction, said second spring being alined with and diametrically opposed to said firstnamed spring and of substantially the same strength as said first-named spring, said firstnamed and said second springs functioning to center said lever on its fulcrum thereby to reduce side friction between said lever and said casing, fluid expansion means for transmitting movement through said second spring to said lever thereby to actuate said lever and said switch, a plunger operatively connecting said fluid expansion means and said second spring, and said first-named spring being adjustable to determine the condition to which said switch will respond.

22. In an automatically operable snap switch, two pairs of switch contacts, two of said contacts being fixed, the other two of said contacts being movable, a lever carrying said movable contacts, said lever being of an insulating material, bifurcated at one end and trifurcated at the other end, a metal U shaped flanged portion partially covering and enclosing the bifurcated end of said lever, said lever being fulcrumed on said metal flange portion and shiftable slightly laterally, a casing enclosing said contacts and said lever and carrying the fulcrum for said lever, a U shaped resilient strip of metal carried by the outer prongs of said trifurcated end portion and carrying said movable contacts, a member having an upturned end portion carried by and affixed to the underside of each of outer prongs of said trifurcated end portion, said upturned end portions having an aperture therethrough receiving the end portion of said resilient metal strips, an adjustment member extending through said member into said outer prongs whereby said member may be adjusted as to tension said resilient metal strip, a magnetic armature carried by the center prong of said trifurcated end portion, a magnet for attracting said armature, said magnet being operable to cause said switch contacts to open and to close with a snap action, said magnet being further operable to cause said movable contacts to be tensioned against said fixed contacts when said switch contacts are closed, and adjustable abutment carrying said magnet, said magnet being adjustable as to vary the tension of the contacts when closed and to vary the amount of travel of the means operating said lever necessary to cause said contacts to snap open or to snap closed, a swivel member carried between the prongs of said bifurcated end portion, a spring positioned against said swivel member and urging said lever in one direction, an adjustable abutment for adjusting the compression of said spring, a plunger positioned against said swivel member in opposition to said spring, a metal bellows surrounding said plunger and affixed to one end thereof, said bellows functioning as a spring means in opposition to said spring and urging said lever in the Opposite direction, said bellows being thermo-responsive to the expansion and contraction of a thermostatic fluid contained therewithin, a supporting member for said spring, a lever arm engaging said supporting member and operable upon movement to control the compression of said spring, a second lever arm for operating said first-named lever arm and including a member for transmitting thrust therebetween, an adjustable screw abutment cooperable with said second lever arm and operable to adjust the same, and said adjustable screw abutment being operable through said first-named lever arm, said thrust member, and said second lever arm to determine the compression of said spring thereby to determine the temperature to which said bellows and said switch will respond.

23. In a device of the character described, a lever shiftable slightly laterally on its fulcrum, supporting means for said lever, a pivoted swivel member carried b said lever, a spring engaging said pivoted swivel member and operable to urge said lever in one direction, an adjustment member engaging said spring and operable to determine the compression of said spring thereby determining the force required to move said lever in opposition to said spring, a second spring engaging said swivel member and alined with and diametrically opposed to said first-named spring, means for transmitting force to said second spring for moving said lever, and said first named spring and said second spring being further operable to maintain said lever centered with respect to the line of thrust of said firstnamed and said second springs.

24. In a snap acting device, a lever adapted for snap movement, said lever being limited in its range of movement, a pivoted member carried by said lever, a spring operatively engaging said pivoted member and urging said lever in one direction, means operatively engaging said pivoted member and urging said lever in the opposite direction, said last-named means being elastic in form, said spring and said elastic means being oppositely alined and operable to center said lever on its fulcrum, a magnet operable to cause said lever to move with a snap action when said lever is within a predetermined distance of one limit of its movement, the force exerted by said elastic means being of a predetermined value to move said lever to said predetermined distance against the opposition of said spring, snap movement of said lever being operable to cause the force exerted by said elastic means against said lever to decrease, the field of attraction of said magnet being such that as said lever moves from said predetermined distance to said one limit of movement the attractive forc between said magnet and said lever increases more rapidly than the force exerted by said elastic means decreases, and said magnet being operable upon decrease of force exerted by said elastic means to hold said lever at said one limit of movement after the force exerted by said elastic means has decreased below said predetermined value until a second predetermined value is reached.

25. In a control device, a control means, a lever operable to move said means, means pivotalls supporting said lever, a rockable abutment member, means carried by said lever adjacent said lever supporting means and pivotally supporting said abutment member for rocking movement on an axis parallel to the axis of movement of said lever, means operable to move said lever in one direction and acting on and in substantially balanced relation to the axis of movement of said abutment member, and an actuating means operable to move said lever in the opposite direction and acting on said abutment member in opposition to and in substantial alinement with the line of thrust of said operable means, said rockable abutment member maintaining the thrust of said operable means and of said actuating means in substantial alinement throughout the range of movement of said lever.

26. In an electric switch, an operating lever,

a U-shaped contact-carrying member of resilient sheet material in overlying substantiall parallel spaced relation to one end of said lever, means securing the base portion of said member to one side of said lever, the legs of said contact-carrying member extending beyond the end or said lever, and a vibration snubbing resilient sheet material member of U-shaped form in substantial registry with said contact-carrying member, means securing the base portion of said snubbing member to the other side of said lever, the free ends of said snubbing member being spaced from said lever for movement and having apertured end portions extending beyond the end of said lever and receiving and confining the free end portions of said contact carrying member.

2'7. In an electric switch, an operating lever, a

U-shaped contact-carrying member of resilient material in overlying substantially parallel spaced relation to one end of said lever, means U shaped form in substantial registry with said contact-carrying member, means securing the base portion of said snubbing member to the other side of said lever, the free ends of said snubbing member being spaced from said lever for movement and having apertured end portions extending beyond the end of said lever and receiving and confining the free end portions of said contact carrying member, a magnetic armature positioned between the legs of said contactcarrying member and carried by said lever, and a magnet adjustably positioned above said armature so that when said lever has moved a predetermined distance toward said magnet the magnetic attraction between said magnet and said armature will cause said lever to move withv a snap action.

28. In an electric switch, a casing having upper, lower, and side walls, an operating lever fulcrumed on said side walls and movable between predetermined limits, a U shaped contact-carrying member of resilient material in overlying substantially paralle1 spaced relation to one end of said lever, means securing the base portion of said member to one side of said lever, the legs of said contact-carrying member extending beyond the end of said lever, a vibration snub-bing resilient member of U shaped form in substantial registry with said contact-carrying member, means securing the base portion of said snubbing member to the other side of said lever, the 1 free ends of said snubbing member being spaced from said lever for movement and having apertured end portions extending beyond the end of said lever and receiving and confining the free end portions of said contact carrying member, a magnetic armature positioned between the legs of said contact-carrying member and carried by said lever, a magnet adjustably carried by said upper wall above said armature so that when said lever has moved a predetermined distance toward said magnet the magnetic attraction between said magnet and said armature will cause said lever to move with a snap action, and a bracket member carried by said upper wall and cooperatively engaging the free end portion of said lever and operable as a slop means for limiting the range of movement of said lever.

29. In a device of the character described, a lever, actuating means operable to move said lever, elastic means operable to transmit the force of said actuating means to said lever, and means determining the extent of stress in said elastic means necessary to move said lever, said last-named means including a spring alined with and opposed to said elastic means and cooperable therewith to maintain said lever centered upon its fulcrum, and means to adjust the compression of said spring.

30. In a device of the character described, a lever, an expansible incompressible means operable to move said lever, a spring for transmitting force from said expansible means to said lever, a second spring alined with and opposed to said first-named spring, an adjustment member for said second spring, and said second spring being adjustable to determine the amount of expansion of said expansible means necessary to move said lever.

31. In an electric switch, an operating lever, a U shaped contact carrying member of resilient material in overlying substantiall parallel spaced relation to one end of said lever, a pivoted member carried by said lever, elastic operating means engageable with one side of said pivoted member for moving said lever, a spring oppositely alined with the point of engagement of said operating means and engaging the other side of said pivoted member to resist movement of said lever, a magnetic armature carried by said lever, and a magnet adjustably positioned above said armature so that when said lever has moved a predetermined distance toward said magnet the magnetic attraction between said magnet and said armature will cause said lever to move with a snap action.

EARNEST J. DILLMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,021,881 North Apr. 2, 1912 1,791,896 Henning Feb. 10, 1931 2,080,169 Dillman May 11, 1937 2,088,556 Dillman July 27, 1937 2,121,079 Eskin June 21, 1938 2,265,495 Shaw Dec. 9, 1941 

